Ammonia and urea excretion in the tidepool sculpin (Oligocottus maculosus): Sites of excretion, effects of reduced salinity and mechanisms of urea transport

摘要: Tidepool sculpins live in a variable environment where water temperature, salinity, gas tensions, and pH can change considerably with the daily tide cycle. are primarily ammoniotelic, 8–17% of nitrogen wastes excreted as urea. The majority net ammonia (Jnetamm; 85%) urea (Jneturea; 74%) excretion occurred across gill, remainder skin, kidney, and/or gut. Acute (2h) exposure to 50% seawater significantly increased Jneturea (2.8-fold), but reduced Jnetamm (3.5-fold). In fish exposed for 1 week, returned control values, remained slightly depressed. Unidirectional influx (Jinurea) efflux (Jouturea) were measured using14C-urea determine if was gills by simple diffusion or carrier-mediated mechanism. Jinurea linear manner increasing levels (0–11 mmol N l−1), while Jouturea independent external concentrations. As well, Jout inurea not different from one another, indicating absence “back transport”. Urea analogs transport inhibitors added did have any consistent effect on unidirectional flux. These results demonstrate that rates sites tidepool very similar those found other marine freshwater teleosts. may play role osmoregulation tissue influenced changes salinity. Finally, we no evidence specific carrier; branchial is likely dependent diffusion.